Conventionally, as such a power output apparatus, there has been known a power output apparatus including an internal combustion engine, two motors, a so-called ravigneaux planetary gear mechanism, a parallel shaft-type transmission capable of selectively coupling two output elements of the planetary gear mechanism to an output shaft (for example, see Patent Document 1). In addition, conventionally, there has been known a power output apparatus including a planetary gear device having an input element connected to an internal combustion engine and two output elements; and a parallel shaft-type transmission having a countershaft connected respectively to a corresponding output element of the planetary gear mechanism (for example, see Patent Document 2). According to the power output apparatus, each of the two output elements of the planetary gear device is fixed respectively to an inner periphery of a corresponding rotor in an electric drive section. Further, conventionally, there has been known a power output apparatus including a power distribution mechanism having an input element connected to an internal combustion engine, a reaction element connected to a first motor generator, and an output element connected to a second motor generator; and two clutches for selectively connecting an axle shaft serving as the output member to between the output element and the reaction element of the power distribution mechanism (for example, see Patent Document 3). According to the power output apparatus, when a first motor generator starts to perform power operation at a negative rotation, the two clutches are controlled so as to connect the reaction element of the power distribution mechanism to the output member and release the connection between the output element and the output member. This can suppress the occurrence of power circulation which causes the first motor generator to be driven by an electric power generated by the second motor generator using part of power of the output member.
[Patent Document 1] Japanese Patent Laid-Open No. 2005-155891
[Patent Document 2] Japanese Patent Laid-Open No. 2003-106389
[Patent Document 3] Japanese Patent Laid-Open No. 2005-125876